This invention relates to deflashing plastic articles and more particularly to trimming moils from the necks of plastic articles with a blade as they sequentially move along a path of travel.
As disclosed in U.S. Pat. Nos. 3,406,598; 3,429,211 and 3,675,521, moils constituting unwanted plastic integrally formed with an article during molding may be removed therefrom in a downstream station by progressively cutting through the plastic as the article is advanced across a blade while engaged between fixed and moving guide members. After such trimming, the articles are usually forwarded to one or more downstream stations where other secondary operations are performed such as quality testing, labeling, decorating, bulk packaging etc.
In systems for continuously manufacturing finished articles employing the aforesaid approach to deflashing, it may occur that downstream equipment at times cannot accommodate the articles issuing from the trimming station, e.g. because of a malfunction of such equipment. Thus, with no place to put oncoming articles, it may be necessary to shut down upstream equipment until the malfunction is corrected, and this reduces the overall efficiency of the manufacturing line even though the upstream equipment is not otherwise associated with the malfunction.
Also, as disclosed in commonly assigned U.S. Ser. No. 467,378, filed May 6, 1974, such aforesaid method of trimming may be effectively used with preforms in a heat-softened condition to remove moils between a preform blow mold and a downstream temperature-conditioning or final molding station. In hot trimming these or other article configurations, the temperature of the plastic in the plane of separation of the moil should be within a certain range or else the article is preferably ejected before reaching the trimming station. But if a substantial number of consecutive articles are outside such range because, for example, of a temporary shutdown of the upstream means responsible for establishing the temperature in the moil-article joint, it will be necessary to continuously cycle the reject means for each consecutive out-of-specification article, and this can create excessive wear of the parts-ejection system, especially at high throughput rates. The previously mentioned considerations with respect to downstream equipment being out of use likewise apply to the temperature-conditioning and final molding stations in this type of hot trimming approach.
In addition, blockage of the trimming system can occur requiring costly downtime for cleanout. For example, the particular part of the article supported between the guide means, such as the neck finish, may have been under-blown in the molding station so that adequate driving force to move it across the trimming blade cannot be developed by the movable guide, and the article therefore hangs up part way across the knife. Or the blade could be sufficiently dull after substantial use such that it will no longer fully penetrate the plastic and a partially trimmed article under such conditions could again hang up part way along the trimming path. In the past such jamming in the trimming station has been alleviated by manually physically prying jammed articles out from between the closely spaced components of the apparatus and this can cause costly damage to the slicing blade.